Hi T,
I had this same error and after weeks of VMWare support giving me the run around, telling me that my drive was failing -- which BTW I had a pretty new computer and only part on the drive was where VMWARE is located i found a link to others who have been having the same issue. Turns out the problem is with VMWARE NOT the drive.
I'e spent weeks without my files, the backup had also been writtent to by VMWARE, lost lots of time unable to answer customers and over $500 doing fixes that their support recommended. I recommend you download WINIMAGE which is free to retrieve your files and get as far away from using VMWARE as you can. I'm moving on to parrallells at this point.
You can see the thread from other users having same issue here http://putraworks.com/2011/05/17/vmware-workstation-operation-on-file-vmdk-failed/
We should really be suing these guys...you can see my error attached.